1. Field of the Invention
This invention relates to non-destructive testing apparatus. More specifically, this invention relates to ultrasonic test and evaluation of general metal cylinders. In particular, the invention relates to an ultrasonic testing and evaluation device for inspecting the SPARROW MK 71/38 warheads.
2. Description of the Prior Art
For several years, the United States Navy has had the problem of being unable to adequately detect critical flaws in the structural integrity of various warheads, especially the SPARROW MK 71/38 warheads. The flaws most commonly occur in the peripheral weldments. These peripheral weldments are critical since they must sustain the high loading forces caused by aircraft launch and by numerous captive flight takeoffs and landings.
Flaw detection was first attempted employing the contact inspection procedure. In this, a hand-held transducer was placed on or about the weldment and then moved about the periphery of the warhead to detect flaws in the peripheral weldments. Since the outer surface of the cylindrical warhead is machined after welding, both initial placement of the transducer and subsequent movement along the approximate line of the weldment were subject to relatively large error. This procedure was limited to detection of total disbondment of the weld.
A second flaw detection approach was employed in which the transducer was suspended on a long, flexible search tube. This tube, however, was adversely affected by vibrations in the water surrounding the test apparatus and the cylinder to be tested. These vibrations were generated by initial immersion of the cylinder in the water; by external disturbances transmitted to the test support stand; and by movement of the search tube itself within the water as it traced the weldment boundary. This limited such instruments to detection of flaws of 0.010 inch or greater. Such tolerances were and are unacceptable for the detection of critical flaws in the structural integrity of the warheads. A device was needed having the capability to detect and evaluate flaws with 0.005 inch accuracy and to provide a permanent record of the test results. The instant invention is directed to that need.
Although the instant invention is used to inspect peripheral weldments on forward and aft ends of the SPARROW MK 71/38 warheads, it has the capability to provide extremely accurate detection and recording on general metal cylinders having solid or axially laminate construction. Employment of the instant invention to such general metal cylinders would be obvious to one skilled in the art of non-destructive testing.